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|
{-# LANGUAGE DeriveDataTypeable #-}
{- -*- Mode: haskell; -*-
Haskell LDAP Interface
Copyright (C) 2005-2009 John Goerzen <jgoerzen@complete.org>
This code is under a 3-clause BSD license; see COPYING for details.
-}
{- |
Module : LDAP.Exceptions
Copyright : Copyright (C) 2005-2009 John Goerzen
License : BSD
Maintainer : John Goerzen,
Maintainer : jgoerzen\@complete.org
Stability : provisional
Portability: portable
Handling LDAP Exceptions
Written by John Goerzen, jgoerzen\@complete.org
-}
module LDAP.Exceptions (-- * Types
LDAPException(..),
-- * General Catching
catchLDAP,
handleLDAP,
failLDAP,
throwLDAP
)
where
import Data.Typeable
import Control.Exception
import LDAP.Types
import LDAP.Data
#if __GLASGOW_HASKELL__ < 610
import Data.Dynamic
#endif
{- | The basic type of LDAP exceptions. These are raised when an operation
does not indicate success. -}
data LDAPException = LDAPException
{code :: LDAPReturnCode, -- ^ Numeric error code
description :: String, -- ^ Description of error
caller :: String -- ^ Calling function
}
deriving (Typeable)
instance Show LDAPException where
show x = caller x ++ ": LDAPException " ++ show (code x) ++
"(" ++ show (fromEnum $ code x) ++ "): " ++
description x
instance Eq LDAPException where
x == y = code x == code y
instance Ord LDAPException where
compare x y = compare (code x) (code y)
#if __GLASGOW_HASKELL__ >= 610
instance Exception LDAPException where
{-
toException = SomeException
fromException (SomeException e) = Just e
fromException _ = Nothing
-}
{- | Execute the given IO action.
If it raises a 'LDAPException', then execute the supplied handler and return
its return value. Otherwise, process as normal. -}
catchLDAP :: IO a -> (LDAPException -> IO a) -> IO a
catchLDAP action handler =
catchJust ldapExceptions action handler
{- | Like 'catchLDAP', with the order of arguments reversed. -}
handleLDAP :: (LDAPException -> IO a) -> IO a -> IO a
handleLDAP = flip catchLDAP
{- | Given an Exception, return Just LDAPException if it was an
'LDAPExcetion', or Nothing otherwise. Useful with functions
like catchJust. -}
ldapExceptions :: LDAPException -> Maybe LDAPException
ldapExceptions e = Just e
#else
{- | Execute the given IO action.
If it raises a 'LDAPException', then execute the supplied handler and return
its return value. Otherwise, process as normal. -}
catchLDAP :: IO a -> (LDAPException -> IO a) -> IO a
catchLDAP = catchDyn
{- | Like 'catchLDAP', with the order of arguments reversed. -}
handleLDAP :: (LDAPException -> IO a) -> IO a -> IO a
handleLDAP = flip catchLDAP
#endif
{- | Catches LDAP errors, and re-raises them as IO errors with fail.
Useful if you don't care to catch LDAP errors, but want to see a sane
error message if one happens. One would often use this as a high-level
wrapper around LDAP calls.
-}
failLDAP :: IO a -> IO a
failLDAP action =
catchLDAP action handler
where handler e = fail ("LDAP error: " ++ show e)
{- | A utility function to throw an 'LDAPException'. The mechanics of throwing
such a thing differ between GHC 6.8.x, Hugs, and GHC 6.10. This function
takes care of the special cases to make it simpler.
With GHC 6.10, it is a type-restricted alias for throw. On all other systems,
it is a type-restricted alias for throwDyn. -}
throwLDAP :: LDAPException -> IO a
#if __GLASGOW_HASKELL__ >= 610
throwLDAP = throw
#else
throwLDAP = throwDyn
#endif
|
